The present invention relates to a numerical controlling device which can greatly improve performances required respectively for various machining without lowering other performances by applying the device to a tooling apparatus for performing the various machining and a tooling apparatus having thereof.
Numerical control in the tooling apparatus is made in such a manner that a cutting tool and machining table are relatively moved along an operating path which is numerically specified previously and that the predetermined machining is given to a workpiece on the machining table. In this kind of the numerical control, in order to satisfy performances required for various machining such as an improvement in machining efficiency, in machining accuracy, and in tool life, a method for optimizing an operating speed of the relative movement has been conventionally suggested as follows.
The first method is adaptive control. In this method, a quantity of state which influences the machining accuracy and the tool life such as a cutting force and a vibration acceleration are detected during actual machining. The operating speed is increased as much as possible under the condition that the detected results do not exceed a predetermined allowable range, and thus the machining efficiency is improved.
The second method is for utilizing a machining condition database. In this method, as for various combinations of the cutting tools and workpieces, machining conditions which respectively conform to the various combinations are previously obtained, and a database is made up by these conditions for the convenience of utilization. And for performing the machining, a corresponding machining condition is read out from the database, and a machining program is automatically created according to the machining condition, and the machining operation is performed according to the machining program.
The third method is a servo parameter adequate selection. In this method, servo parameters which were previously determined in the servo units of the numerical controlled tooling apparatus is selected according to characteristics of individual tooling apparatuses, and while the machining accuracy is being improved by reducing a tracking error, to improve the machining efficiency.
However, in the first method, a sensor, which accurately detects a quantity of state required for the detection of the cutting force and vibration acceleration with satisfactory practical sensitivity, has not been introduced for practical use. For this reason, when the operating speed is determined based on the inaccurately detected result of the sensor, in order to take precautions against possible accidents such as damages to the cutting tools, it is necessary to expect a sufficient safety factor, and thus the improvement in the machining efficiency cannot be expected.
In addition, the machining condition database used in the second method is arranged so as not to substantially require input of the machining conditions for each machining but so as to expect safety for wide application to the combinations of the cutting tools and workpieces. For this reason, even if the machining operation is performed according to the database, there arises a problem that the machining efficiency is not improved.
Moreover, in the third method, the servo parameters to be selected are limited to a velocity loop gain used in determining the operating speed. In addition, this selection is performed without considering a difference in a degree of importance according to types of machining with respect to the required performances (machining efficiency, machining accuracy, and tool life, etc.), so a degree of improvement in an actually obtained tracking error is small (approximately 20 to 30%).
In the aforementioned conventional methods, an improving effect to be expected is generally small. For example, when a high-powered tooling apparatus which is feasible for the high machining speed and cutting tools with high rigidity are used, similar or better effects can be obtained more securely and easily. Therefore these methods have been hardly practiced in the present situation.
Moreover, the machining condition database used in the second method should be updated at each time according to an improvement in the machining technologies such as development of new materials for the tools, so if this update is neglected, the machining efficiency is lowered otherwise.
The present invention has been made with the aim of solving the above problems, and it is one object of the present invention to provide a numerical controlling device in which performances required for various machining using a tooling apparatus can be greatly improved according to a difference in a degree of importance with respect to types of the machining, and thus high machining efficiency and high machining accuracy can be simultaneously obtained by adopting the device, and a tooling apparatus having thereof.
The numerical controlling device of the present invention used in a tooling apparatus in order to move a cutting tool and/or a machining table along an operating path which is previously numerically specified and to give a predetermined machining to a workpiece on the machining table by bringing the cutting tool into contact with the workpiece, characterized in that a control parameter relating to an operating speed and operating position is selected based on a predetermined database in order to obtain an adequate operating speed and operating position through the entire operating path during machining and non-machining, according to a specification of types of the cutting tool and/or workpiece, and of a machining mode including the operating path.
According to the present invention, as for the types of the cutting tool and/or workpiece as well as the operating path of the cutting tool and/or the machining table, namely, the xe2x80x9cmachining modexe2x80x9d, the control parameter relating to the operating speed and operating position is previously obtained through the entire operating path during machining and non-machining, and the database is produced with the parameter. At the time of performing the machining, the control parameter corresponding to the specified machining mode is selected, and the operation is done by a servo unit according to the control parameter. Therefore, the high machining efficiency and high machining accuracy can be obtained simultaneously.
Another numerical controlling device of the present invention is characterized in that the control parameter includes a position loop gain to be multiplied in order to obtain a position changing command based on an operating position command and a velocity loop gain to be multiplied in order to obtain an operating speed command based on the obtained position changing command.
According to the present invention, the velocity loop gain as the control parameter relating to the operating speed and the position loop gain as the control parameter relating to the operating position is included respectively into each control parameter. Therefore, the position accuracy is improved and the operating speed is increased at the same time, and thus the machining accuracy can be maintained and the machining efficiency can be improved simultaneously.
Still another numerical controlling device of the present invention is characterized in that internal state of the servo unit for operating the cutting tool and/or the machining table are detected and stored data in the database are updated based on the detected result.
According to the present invention, the internal state of the servo unit of the tooling apparatus during machining operation is detected by a suitable sensor wherein the internal state is such as a driving electric current of a driving motor of the cutting tool and/or the machining table. If this detected result has a predetermined margin, the stored data in the database is updated according to the result. Therefore, the database can be prevented from becoming obsolete due to improvement in machining technologies.
Still another numerical controlling apparatus of the present invention is characterized in that the updating means includes a display unit for displaying that the updating is possible and an input unit for accepting an operation by an operator. Moreover, the updating is performed based on a predetermined operation on the input unit operated according to the display on the display unit.
According to the present invention, when the updating means is in the enable state of updating the database, this state is displayed on the display unit. As a result, this induces the operator to perform a confirming operation. Only when this operation is performed, the updating is performed. Therefore, inadequate updating due to disturbance such as detection failure by the sensor or idle updating can be prevented.
Still another numerical controlling device of the present invention is characterized in that just when the cutting tool and/or the machining table reach an end position of the operating path, they are operated in a direction opposite to that of the operation until reaching the end position.
In addition, still another numerical controlling device of the present invention is characterized in that a time constant of the velocity loop is selected so that a time constant of the position loop is decreased as small as possible and machining time based on the time constant of the position loop becomes minimum.
According to these invention, by performing the opposite operation at a speed as fast as possible, the machining time becomes the shortest at the time when the cutting tool reaches the end position of the operating path, and thus time that the cutting tool slips (xe2x80x9crubsxe2x80x9d) against the workpiece can be reduced.
The tooling apparatus of the present invention has the numerical controlling device with the aforementioned arrangement, and performs a predetermined machining according to a control command from the numerical controlling device.
According to the present invention, since the predetermined machining is performed by using the numerical controlling device, the aforementioned effects of the numerical controlling device can be obtained as the tooling apparatus.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.